Clean potatoes. Remove outside skin on onion. Dice onion and potatoes, leaving skins on. Place them in microwave-proof bowl and mix in garlic, pepper and salt. Put in microwave on high for 6-8 minutes. Stir and check for potato softness. The pototoes should be slightly crisp, but not crunchy.
Chop sundried tomatoes, and set aside.
Ten minutes prior to serving, place oil and sherry into fry pan. Add potato mixture and fry, stirring occasionally. Add in sundried tomato and rosemary. Fry for 5-10 minutes, until potatoes are soft, and well cooked.